Tropical tropopause parameters derived from GPS radio occultation measurements with CHAMP

[1] The temperature structure in the tropical upper troposphere and lower stratosphere (UTLS) region is discussed based on Global Positioning System (GPS) radio occultation (RO) data from the German CHAMP (CHAllenging Minisatellite Payload) satellite mission. Several climatologies for tropopause parameters based on radiosonde data and model analyses have been published in recent years. Both data sources suffer either from low global coverage or poor vertical resolution. The GPS RO technique, on the other hand, is characterized by global coverage, high vertical resolution, all-weather viewing, and long-term stability. CHAMP RO data are available since February 2001. Since May 2001, up to 200 high- resolution temperature profiles per day are available. The temperature bias between CHAMP temperature profiles and radiosonde data as well as ECMWF analyses is less than 0.5 K between 300–30 hPa. On the basis of the May 2001 to November 2003 data set of CHAMP RO data the structure and temporal and spatial variability of the tropical tropopause based on several tropopause definitions (thermal and cold-point tropopause) are discussed. This includes an overview of the global tropopause characteristics, the discussion of the annual cycle and the latitudinal-longitudinal structure of the tropical tropopause. In the CHAMP RO temperature data, clear evidence of the stratospheric quasi-biennial oscillation (QBO) was found. The goal of this study is to show the potential of GPS RO for global monitoring of the temperature demonstrated exemplarily for the tropical UTLS region and based on the first 31 months (as of November 2003) of CHAMP RO data.

[1]  W. G. Melbourne,et al.  The application of spaceborne GPS to atmospheric limb sounding and global change monitoring , 1994 .

[2]  Rolf König,et al.  The Radio Occultation Experiment aboard CHAMP: Operational Data Analysis and Validation of Vertical Atmospheric Profiles , 2004 .

[3]  GPS ground station data for CHAMP radio occultation measurements , 2001 .

[4]  Steven Businger,et al.  GPS Sounding of the Atmosphere from Low Earth Orbit: Preliminary Results , 1996 .

[5]  Lennart Bengtsson,et al.  GNSS Occultation Sounding for Climate Monitoring , 2001 .

[6]  A. Gettelman,et al.  Distribution and influence of convection in the tropical tropopause region , 2002 .

[7]  Richard Swinbank,et al.  Global QBO Circulation Derived from UKMO Stratospheric Analyses , 1999 .

[8]  Fei Wu,et al.  Interannual variability of the tropical tropopause derived from radiosonde data and NCEP reanalyses , 2000 .

[9]  D. Seidel,et al.  Climatological characteristics of the tropical tropopause as revealed by radiosondes , 2001 .

[10]  Christian Rocken,et al.  Seasonal and Longitudinal Variations in the Tropical Tropopause Observed with the GPS Occultation Te , 2000 .

[11]  Robert Sausen,et al.  Behavior of tropopause height and atmospheric temperature in models, reanalyses, and observations: Decadal changes , 2003 .

[12]  Klaus P. Hoinka,et al.  Statistics of the Global Tropopause Pressure , 1998 .

[13]  Minghua Zhang,et al.  Cooling trend of the tropical cold point tropopause temperatures and its implications , 2001 .

[14]  Chidong Zhang.  On the Annual Cycle in Highest, Coldest Clouds in the Tropics , 1993 .

[15]  Kevin Hamilton,et al.  The quasi‐biennial oscillation , 2001 .

[16]  R. Garcia,et al.  Time-dependent upwelling in the tropical lower stratosphere estimated from the zonal-mean momentum budget , 2002 .

[17]  Brian J. Hoskins,et al.  The tropical tropopause , 1998 .

[18]  Christian Rocken,et al.  Applications of COSMIC to Meteorology and Climate , 2000 .

[19]  P. Forster,et al.  A Climatology of the Tropical Tropopause Layer , 2002 .

[20]  G. Craig,et al.  Stratospheric Influence on Tropopause Height: The Radiative Constraint , 2000 .

[21]  R. J. Reed,et al.  The Annual Temperature Variation in the Lower Tropical Stratosphere , 1969 .

[22]  Rolf König,et al.  Atmosphere sounding by GPS radio occultation: First results from CHAMP , 2001 .

[23]  Rolf König,et al.  GPS radio occultation with CHAMP: an innovative remote sensing method of the atmosphere , 2004 .

[24]  A. Gettelman,et al.  Horizontal transport and the dehydration of the stratosphere , 2001 .

[25]  M. Hitchman,et al.  The stratospheric quasi-biennial oscillation in the NCEP reanalyses: Climatological structures , 2001 .

[26]  Jens Wickert,et al.  Validation and Data Quality of CHAMP Radio Occultation Data , 2003 .

[27]  Fei Wu,et al.  Thermal variability of the tropical tropopause region derived from GPS/MET observations , 2003 .

[28]  Robert Sausen,et al.  Use of Changes in Tropopause Height to Detect Human Influences on Climate , 2003 .

[29]  Anthony J. Mannucci,et al.  CHAMP and SAC-C atmospheric occultation results and intercomparisons , 2004 .

[30]  J. Schofield,et al.  Observing Earth's atmosphere with radio occultation measurements using the Global Positioning System , 1997 .

[31]  J. Holton,et al.  Stratosphere‐troposphere exchange , 1995 .

[32]  C. Peña-Ortiz,et al.  The stratospheric QBO signal in the NCEP reanalysis, 1958–2001 , 2003 .

[33]  J. Wallace,et al.  On the cause of the annual cycle in tropical lower-stratospheric temperatures , 1994 .

[34]  G. Craig,et al.  GCM Tests of Theories for the Height of the Tropopause , 1997 .

[35]  K. Gage,et al.  The tropical tropopause over the western Pacific: Wave driving, convection, and the annual cycle , 1996 .

[36]  Minghua Zhang,et al.  Tropical Cold Point Tropopause Characteristics Derived from ECMWF Reanalyses and Soundings , 2001 .

[37]  X. Zou,et al.  Analysis and validation of GPS/MET data in the neutral atmosphere , 1997 .